Preformulation work for the tableting of a spray-dried Visci Herba dry extract, typically supplied at a native extract ratio of 4:1 with residual moisture below 5.0% w/w, begins with dry granulation rather than direct compression. A roller compactor fitted with 1.0–1.5 mm milling screens is used because the hygroscopic amorphous fraction lowers the glass transition temperature and increases sticking tendency on direct-compression tooling. A representative tablet core contains 25–35% w/w Visci Herba dry extract, 30–40% w/w microcrystalline cellulose, 15–20% w/w dibasic calcium phosphate dihydrate, 5–8% w/w crospovidone, and 0.8–1.2% w/w magnesium stearate. Pre-blending is conducted in a bin blender for 15 minutes at 12 rpm, followed by roller compaction at 18–25 kN roll force and 4–6 kN pre-compaction, with fines recycling limited to 20% of total granulate mass. The dried granulate at 2–4% w/w moisture is compressed on a rotary tablet press at 8–14 kN main compression and 2–3 kN pre-compression. Tablets are film-coated with an aqueous HPMC-based coating at 3–4% w/w weight gain and tested for friability per Ph. Eur. 2.9.7 with a limit of NMT 1.0%, uniformity of mass per Ph. Eur. 2.9.5, and dissolution per Ph. Eur. 2.9.3 using apparatus II at 50 rpm in 900 mL purified water at 37.0 ± 0.5°C. The terminal product is an immediate-release veterinary tablet; published data for dissolution acceptance limits specific to Visci Herba tablet formulations is limited and must be established from pilot-lot data.

What Limits Filterability and Sterile Filtration Throughput for Aqueous Viscum album L. Injectable Solutions?

In injectable production, aqueous Visci Herba extracts are processed at a dry extract equivalent concentration of 1.0–5.0 mg/mL, adjusted with sodium chloride to 0.9% w/v tonicity and buffered at pH 5.5–6.5. The solution is clarified through a 0.45 µm polyethersulfone membrane under 0.5–0.8 bar differential pressure before sterile filtration through a 0.22 µm sterilizing-grade polyvinylidene fluoride membrane. Polysaccharide and glycoprotein fractions raise dynamic viscosity, especially when the extraction solvent contains more than 30% v/v ethanol, and the resulting filter capacity at scale cannot be predicted from small-batch viscosity alone. Where terminal steam sterilisation at 121°C is omitted, the justification typically includes thermosensitivity of viscotoxin-containing fractions and limited published data on terminal sterilisation of this extract; aseptic filtration remains the standard terminal sterilisation route. The filtered solution is filled into amber glass vials under nitrogen headspace at 10 mL or 20 mL fill volume and sealed with Halobutyl rubber stoppers. Sterility is verified per Ph. Eur. 5.1.1, bacterial endotoxin is measured per Ph. Eur. 2.6.14 with a limit of NMT 0.5 EU/mg unless otherwise justified, and particulate contamination is assessed per Ph. Eur. 2.9.19. Filter sizing for each batch is confirmed by Vmax testing because published filter capacity data for this specific extract configuration is limited. The terminal product is a clear to slightly opalescent aqueous injectable solution for veterinary parenteral administration.

Capsule Filling Uniformity and Moisture Control in Milled Visci Herba Fractions

Milled Visci Herba dry extract intended for capsule filling is preconditioned at 20–25°C and 30–40% RH because the amorphous fraction adsorbs moisture above 45% RH and becomes tacky on dosator pins. The capsule fill formulation contains 40–60% w/w Visci Herba dry extract, 30–45% w/w lactose monohydrate, 5–10% w/w pregelatinised starch, 0.5–1.0% w/w colloidal anhydrous silica, and 0.5–0.8% w/w magnesium stearate. The blend is passed through a 0.5 mm stainless steel sieve and mixed in a V-blender for 10 minutes at 25 rpm; the sieve fraction below 75 µm is held at ≤ 30% to avoid fluidisation during filling. Capsule filling is performed on a dosing-disc or dosator machine at a target fill weight requiring ±5% weight variation, using size 0 or 1 hydroxypropyl methylcellulose capsules when a non-gelatin shell is specified. In-process checks include fill weight every 30 minutes and moisture by loss on drying per Ph. Eur. 2.2.32. Release testing includes uniformity of mass per Ph. Eur. 2.9.5 and disintegration per Ph. Eur. 2.9.1; dissolution testing per Ph. Eur. 2.9.3 is added where the capsule is intended for immediate release in companion animals. Published data for capsule-specific dissolution acceptance limits for Visci Herba is limited and usually derived from tablet data rather than capsule data. The terminal product is a hard capsule with low fill-weight variability and controlled moisture uptake.

When an orally administered powder or granule is required for in-feed or drinking-water delivery, the extract is converted into a free-flowing granulate by fluid-bed top-spray granulation rather than simple blending. The formulation contains 10–25% w/w Visci Herba dry extract, 60–80% w/w dextrose monohydrate or maltodextrin, 3–5% w/w povidone K30 as binder solids, and 0.5–1.0% w/w colloidal anhydrous silica as anti-caking agent. Inlet air temperature is held at 55–65°C, product bed temperature at 30–35°C, atomising air pressure at 1.2–1.8 bar, and spray rate adjusted to maintain granule moisture at ≤ 4.0% w/w. The dried granules are sieved to a target fraction of 125–500 µm, with oversize milled through a 1.0 mm screen and fines below 100 µm recycled at ≤ 15%. Water dispersibility is tested by adding a 5 g sample to 200 mL water at 20°C; complete wetting is checked against a specification of 60 seconds without lumping. Particle-size distribution is measured per Ph. Eur. 2.9.12, microbial quality per Ph. Eur. 5.1.4, and loss on drying per Ph. Eur. 2.2.32. The terminal product is a water-dispersible granulate packaged in aluminium-laminated pouches for oral administration via feed or drinking water.

When Premix Carrier Selection Dictates Blend Uniformity and Carryover Risk in Feed-Grade Production

The choice of carrier in feed-grade premix production is governed by particle-size overlap with the milled extract, dust retention, and electrostatic charge. Visci Herba dry extract is incorporated at 1–10% w/w into a carrier base of calcium carbonate with median particle size 150–250 µm for dense premixes, or wheat middlings when the premix must remain homogeneous after pneumatic conveying. The complete-feed inclusion rate is typically 0.5–2.0 kg/tonne, which places the working extract concentration in the final feed below 100 mg/kg for most formulations. Mixing is performed in a ribbon blender at 60–70% working capacity for 15–20 minutes, with a coefficient of variation target of CV ≤ 5% based on 10 sampling points. Segregation testing is conducted after discharge because fines can migrate when carrier density exceeds 1.2 g/cm³. Dust extraction must be isolated from the mixing chamber to avoid loss of fine extract fractions above 0.3 g/m³ airborne dust. Release and retention sampling follow 21 CFR Part 225 current good manufacturing practice for medicated feeds, and the site operates under ISO 22000 with HACCP prerequisite controls. The terminal product is a free-flowing feed premix in 25 kg polyethylene-lined bags, intended for dilution into complete feed at the point of mixing.

Preservative Partitioning Into Micellar Fractions Compromises Oral Solution Stability Below pH 4.5

For oral solution preparation, the extract is diluted to a dry extract equivalent of 5–20 mg/mL in a vehicle containing sorbitol 20–30% w/v, glycerol 10–15% w/v, and purified water. The pH is adjusted to 5.0–6.0 with citrate buffer; below pH 4.5, the aqueous solubility of phenolic fractions decreases and flocculation may appear. Potassium sorbate at 0.1–0.2% w/v or sodium benzoate at 0.05–0.1% w/v is used as preservative, but preservative partitioning into poorly soluble micellar fractions must be confirmed by chemical recovery studies. The solution is prepared in a stainless steel vessel with a propeller stirrer at 200–300 rpm, passed through a 5 µm polypropylene depth filter, and filled into amber glass bottles with polyethylene dosing caps. In-process testing includes pH, relative density per Ph. Eur. 2.2.5, and visual clarity; preservative efficacy is evaluated per Ph. Eur. 5.1.3 and microbial quality per Ph. Eur. 5.1.4. Light protection is required because flavonoid fractions in the extract are light-sensitive, and published data for this specific Visci Herba oral solution configuration is limited. The terminal product is an oral solution for dilution or direct administration through calibrated dosing devices.